A method, consisting of presenting on a display screen a graphical image of a heart of a patient, including icons representing a catheter that is positioned within the heart and an electrode on the catheter, while the electrode is in contact with tissue at a location in the heart. The method further includes acquiring, using the electrode, electrical signals from the tissue at the location, and processing the acquired signals so as to detect an occurrence of a predefined signal feature in the acquired signals. The method also includes, upon detecting the occurrence of the predefined signal feature, modifying a visual feature of at least one of the icon representing the electrode and the icon representing the catheter on the display screen.
